PE EIE[R-Rg RESEARCH ON - HJ Andrews Experimental Forest

where C is the percentage cover by epiphytes ,
r is the radius at the base of the axis, and h i s
the length of the axis . The bulk of epiphyte
biomass for these branch systems is assume d
to occur on the axes; if this is not the case ,
the biomass of epiphytes on the many small
branch systems, which are made up entirely
of branchlets, may be significantly underestimated
.
Since EIV is based partly on subjective estimates
of length of axes and percentage cove r
by epiphytes, the relationship between EI V
and epiphyte biomass may be expected t o
vary from worker to worker and from sampling
period to sampling period, and for thi s
reason will be treated separately for each tree .
However, it should be possible to correct
importance values so that correlations may be
obtained that will hold across a set of trees .
Sampling Branch Systems
The basic sampling unit for epiphytes o n
axes in the branch systems is a "cylindrat, "
which is analagous to a quadrat but runs completely
around the axis so that two edges ar e
fused . Our 1 dm cylindrats include the entir e
surface for a distance of 1 dm along an axis .
Thus the surface area of the cylindrat varies ,
depending on the diameter of the axis in th e
region sampled .
Cylindrats were spaced along an axis with a
distance of 4 dm from the center of on e
cylindrat to the center of the next . Th e
distance from the trunk to the first cylindra t
sampled along a main axis was varied from 0
to 1, 2, and 3 dm so as to avoid errors whic h
would be introduced by horizontal zonation
on the axis near its origin from the trunk .
Estimates of epiphyte cover were made, an d
then the epiphytes were stripped from th e
cylindrat and bagged . Axis diameter at th e
center of each cylindrat was measured t o
enable calculation of surface area of the axes .
Branchlets (